2. Requirements¶
2.1. Basic requirements¶
Structures and structural elements shall be designed, constructed and maintained in such a way that they are suited for their use during the design working life and in an economic way.
In particular they shall, with appropriate levels of reliability, fulfil the following requirements:
They shall remain fit for the use for which they are required (serviceability limit state requirement)
They shall withstand extreme and/or frequently repeated actions occurring during their construction and anticipated use (ultimate limit state requirement)
They shall not be damaged by accidental events like fire, explosions, impact or consequences of human errors, to an extent disproportionate to the triggering event (robustness requirement, see Annex A).
2.2. Reliability differentiation¶
The expression “with appropriate levels of reliability” used above means that the degree of reliability should be adopted to suit the use of the structure, the type of structure or structural element and the situation considered in the design, etc.
The choice of the various levels of reliability should take into account the possible consequences of failure in terms of risk to life or injury, the potential economic losses and the degree of social inconvenience, as described in chapter 8. It should also take into account the amount of expense and effort required to reduce the risk of failure. It is further noted, that the
term “failure” as used in this document refers to either inadequate strength or inadequate serviceability of the structure.
The consequences of a failure generally depend on the mode of failure, specially in those cases when the risk to human life or injury exists.
In order to provide a structure corresponding to the requirements and to the assumptions made in the design, appropriate quality measures shall be adopted. These measures comprise definition of reliability requirements, organisational measures and controls at the stages of design, execution and use and the maintenance of the structure.
2.3. Requirements for durability¶
The durability of the structure in its environment shall be such that it remains fit for use during its design working life. This requirement can be considered in one of the following ways:
a) By using materials that, if well maintained, will not degenerate during the design working life.
b) By giving such dimensions that deterioration during the design working life is compensated.
c) By chosing a shorter lifetime for structural elements, which may be replaced one or more times during the design working life.
d) By inspection at fixed or condition dependent intervals and appropriate maintenance activities.
In all cases the reliability requirements for long and short term periods should be met. Analysis aspects on durability are described in Annex B.